Regulating means for a gas piston operated gun



Dec. 29, 1959 B. MAILLARD 2,918,848

REGULATING MEANS FOR A GAS PISTON OPERATED GUN Filed July 9, 1956 nninww Z 12 J2 J3 QUINE w\ I 5 "WI-TI IIIIII United States Fatent Cbarrel and the outside, generally at right angles. tothe barrel axis,for feeding some amount of powder gases,

immediately after the projectile has moved beyond the;

gas tap, to a device operated by the pressure of said gases and whichcooperates in the automatic operation of the gun.

It is well known that with such guns; when a long burst is fired, thegun being initially cold, the rate of fire varies during the burst dueto the modifications in the firing conditions caused by the heating ofsome parts of the gun (which heating causes said parts to expand,modifies the lubricating conditions and so on). This variation of therate of fire which, in fact, is an increase of said rate, may causeserious damages when a very long burst is fired. As a matter of fact,the parts of the gun are adjusted to give initially, that is to say whenthe gun is cold and even at low temperatures, the normal rate of fire,and an increase of said rate beyond a given value may have seriousconsequences on the operation of the gun and in particular of thecartridge feed device thereof.

The object of my invention is to obviate this drawback.

For this purpose, I provide, between the gas tap and the device to beoperated by the powder gases under pressure, heat responsive valve meansarranged to control the passage through which said gases can flow so asto vary the cross section of said passage in response to variations inthe temperature of operation of at least one part of the gun.

A preferred embodiment of the present invention will be hereinafterdescribed with reference to the accompanying drawing given merely by wayof example and in which:

Fig. 1 is a vertical sectional view of "aportion of an automatic gunmade according to my invention.

Fig. 2 is a similar view on an enlarged scale of part of the structureof Fig. 1. I I

Fig. 3 is a view similar to Fig.2 showing a modification.

Fig. 4 is an explanatory diagram to' be referred to hereinafter.

The automatic gun shown on the drawing includes a barrel 2 provided witha gas tap 1 through which the powder gases are fed to a cylindricalcavity formed in a support 9 and one end of which constitutes acylindrical chamber 3 in which is slidable a piston 4 which constitutesa power element for controlling for instance the release of the gunbreech block (not shown on the drawing). 3

In order to prevent an undesirable rise of the rate of fire of this gunwhen a long burst is fired, I provide, in the construction of Figs. 1and 2, acore 5 housed in a cylindrical portion of said cavity adjoiningchamber 3, said core being mounted with a suitable annular clearance iev . Z, hetweeni its periphery and. the: wall of said cylindricalicavity portion, asvisible at 6'. The gases from tap=1 conveyed through aconduit 7 to the above mentioned. bore upstream of said annular passage6 so that they must flow through said passage in: order to reach chant!bet- '3.

Said-core is carried by a plug 8 screwed in the support I 9 in which thecavity is formed, conduit 7 being alscr formed: in said support 9; Theleft hand portion of plug. 8 may be provided with a blind hole 10intended to facilitate cooling thereof.

With such an arrangement, core 5 may be considered. as a kind ofthrottlevalve member expansible in response toits being heated so as tomodify the cross section. of passage 6. Thisresult is due to the factthat, plug, 8 and; support; 9 being for instance both: made of steel,whena relatively long burst (for instance shots) is fired, core 5expands more rapidly than the cylindrical. wall ofi the bore in which itis housed in support 9 so that the. cross section of annular passage 6decreases, which tends to reduce the rate of. fire; The materials ofwhich sup-= port 9 and the core 5 are made may be chosen so that thecore expands: more rapidly than the support 9.

In actual practice, it may often happen that this: cross section:reduction is: toov great and that, despite the tendency of the gun tohave its rate of fire increased as a consequence of itsbeing heated up,the rate of. fire actually decreases due to too great a reduction of thecross section of passage 6. In order to overcome this drawback, itsuflices to provide through core 5 passages 11 through which a portionof the gases flows directly from conduit 7 into chamber 3.

On Fig. 4, I have plotted in abscissas the temperatures and in ordinatesthe cross sections through which the gases can flow. The lower rectanglecorresponds to passages 11 whereas the trapezium above this rectanglecorresponds to the variable cross section of annular passage 6. It isthus possible, by suitably choosing the initial cross sections, toobtain the desired relative variation of the total cross section whenthe arm is heating by firing.

In the modification of Fig. 3, passage 7 opens directly into acylindrical bore 12 provided in support 9, the end 13 of this bore beingof frusto-conical shape and communicating witha passage 14 leading tochamber 3, the whole of bore 12, passage 14 and chamber 3 forming theabove mentioned cavity.

A hollow plug 15 having a nut-shaped head 16 is screwed in cylindricalbore 12 and the end 17 of said plug is conical, shaped so that when plug15 has been screwed in position, this point 17 is located opposite thefrusto-conical end 13 of bore 12 and leaves, between 13 and 17, anannular passage 18 of suitable cross section.

When a long burst is fired, rod 17 is heated and expands quicker thanmember 9 so that the cross section of annular passage 18 decreases. Thelefthand portion of the rod 17 may be provided with a blind hole ,20 incommunication with the atmosphere.

The result is the same as with the arrangement of Fig. 2. In this casealso, passages 19 of suitable constant cross section may be providedeither in the end of rod 17 or in the portion 13 of the support, so asto ensure the desired variation of the rate of fire.

In a general manner, while I have, in the above description, disclosedwhat I deem to be practical and eflicient embodiments of my invention,it should be well understood that I do not wish to be limited thereto asthere might be changes made in the arrangement, disposition and form ofthe parts without departing from the principle of the present inventionas comprehended within the scope of the accompanying claims.

What I claim is:

1. An automatic gun comprising, in combination, a barrel provided with agas tap,'means carried by said barrel forming a chamber communicatingwith saidsgas tap wherebygases flow from said gas tap into said chamberevery time a shot is fired, a pistonvmovable in said chamber in responseto pressure rises therein, and valve means interposed between said gastap and said chamber for varying the flow of gases from said gas tap tosaid chamber, said valve means comprising awplug mounted in said chamberand having a free end of lessened diameter extending toward said pistonbeyond said gas tap so as to always leave an annulartpassage between thefree end of said plug and the walls of said chamber for the passage ofgases from said gas tap to said chamber, said free end being expansibleunder the efiect of heating by the gases flowing from said gas tap tosaid chamber during a burst of firing of the gun, whereby thecross-section of said annular passage is reduced as the burst becomeslonger and longer, said plug being further provided with at least oneother passage between said gas tap and said chamber and formed in saidfree end so that its cross-section is but little varied by thermalexpansion of the free end of said plug.

2. An automatic gun according to claim 1 wherein said plug is providedwith a blind hole in communication withthe atmosphere. 7

3. An automatic gun which comprises in combination a barrel providedwith a gas tap, means carried by said barrel forming a cavity incommunication with said gas tap whereby powder gases flow from saidbarrel to said cavity every time a shot is fired, one end of said meansmeans at the end of said cavity opposed to that formed by said chamber,said rod extending toward said'partition beyond said gas tap to alwaysleave an annular passage between the free end of said rodand the wall ofsaid partition, said. free end being expansible under the efl ect ofheating by the gases flowing from said cavity to said chamber during aburst of firing of the gun, whereby the crosssection of said annularpassage is reduced as the burst becomes longer and longer.

4. An automatic gun according to claim 3 wherein said rod is providedwith a blind hole in communication with the-atmosphere.

5. An automatic gun according to claim 3 and further including at leastone passage in parallel with said ann'ular passage and formed so thatits cross-section is but little varied by thermal expansion.

References Citedin the file of this patent UNITED STATES PATENTS 795,627Larsson July 25, 1905 804,986 Stamm Nov. 21, 1905 960,825 Colleoni June7, 1910 l l l

